parallel master tests using nextest

.github/workflows/ci.yml

@@ -137,6 +137,16 @@ jobs:
           command: install
           args: cargo-hack
 
+      - name: Generate Cargo.lock
+        uses: actions-rs/cargo@v1
+        with: { command: generate-lockfile }
+
+      - name: Tweak lockfile
+        uses: actions-rs/cargo@v1
+        with:
+          command: update
+          args: -p=rustls --precise=0.20.2
+
       - name: tests
         run: |
           sudo bash -c "ulimit -Sl 512 && ulimit -Hl 512 && PATH=$PATH:/usr/share/rust/.cargo/bin && RUSTUP_TOOLCHAIN=1.46 cargo ci-test-lower-msrv"